@tux1337 (not sure which feature you are referencing here as @Dragon2611’s original post, which started this thread, mentions sub-volume level of encryption. This is not something that is currently supported by btrfs, although I believe it’s planned. But as @Dragon2611 states:
which was a sentiment shared by the Rockstor development team and is now something that is supported by Rockstor, both in the stable and release channel updates, as of version:
and the relevant docs mentioned in that release announcement are available in the official docs at: LUKS Full Disk Encryption
Hope that helps by way of an update and apologies to @Anders for not updating this thread in a more timely manner.
Oh well, bit by bit.